Event Duration Measurement (EDM) in Combined Sewer Overflow (CSO) applications has, rightly, become a significant focus for our water operators. Management of pollution under flood conditions is a significant challenge and, with ever more demanding monitoring regimes, operators have implemented thousands of CSO monitoring installations and thousands more are planned, with data logging and level measurement to record spill events. Looking beyond CSO, there are good reasons to monitor flow throughout the waste water network to identify problem areas and inform maintenance regimes.
Level is only one part of the equation, and so companion instruments can be positioned above a channel to measure the flow velocity.
Measuring velocity using a non-contacting technique is a very complex challenge analytically and has only really become realistic with the faster processors now available to instrumentation designers. Pulsar use a technique called RSSA (Refracted Spread Spectrum Analysis). In Pulsar’s MicroFlow product, a pulse is fired at the liquid surface, producing a mass of reflections from the full width of the channel, a single transducer handling channels up to 1.5m width and multiple transducers working together for wider applications, applying the RSSA algorithms to analyse and integrate the received signals, then ‘slicing’ them for real-time analysis and velocity calculation. MicroFlow can also be used as a stand-alone device that delivers velocity data via RS485 Modbus.